Mismatched Split Central Unit Partially Freezing Up/ Not Cooling!

[ttuee2006]

When I bought this house back in 2006 it had the original Builder's unit Goodman POS heatpump in it. After having nothing but crap from the control boards, stuck reversing valves, failed condenser fan motors, etc, I had the crap-tastic condenser unit yanked out and replaced with a Ruud. Why Ruud? We've had them at work, at my parent's house, at my apartments, etc and never once in 15 years had a single problem.

Long story short, this house still has the original interior Goodman air handler and coil assembly, but the Ruud outdoor unit. I have no idea what the original SEER rating was on the Goodman, but the Ruud is a 13. Both matched in size for a 2.5 Ton unit.

The problem started about a week ago when I started noticing the A/C running almost continuously. Its been intermittently hot so its already been A/C season for the past couple of months here. Originally you could hear "splashing" and "surging" in the A/C lines in the wall fairly frequently, but the thing cooled just fine and hardly ran.

In the last 2 days though I've noticed it running almost all day long and the house not being comfortable anymore. T-Stat set at 74, house sitting at 76-77 all the time. I also noticed reduced air flow through the vents.

Like any dutiful Grasshopper, I checked the air filter- clean, checked for leaks in the ductwork - none, checked for junk in the condenser or a stuck fan - nothing. Pulled the cover off the evaporator in the attic (this is a horizontal unit) and noticed that 2 of the lines running to the suction line were frosted. The rest weren't, and 2 of them were not even cold.

Since this is the world's most poorly designed air-handler ever, half the evaporator coils sit in the condensation pan all the time half covered with water, and the other half you can actually see. There was a visible band of ice towards the lower side of the coil, with the rest of the coil being cool, but not cold.

In addition to this, when kicking the unit on, you can hear the gurgling/splashing noises in the lines for about 4-10 seconds, then you hear the refrigerant start flowing solidly, no more splashing/gurgling like it did before. You can also hear the compressor sort of load up outdoors.

I'm thinking restriction or ice forming in the lines, but this thing's got a bi-directional filter/drier in-line outside. I'd think that should have taken care of any debris floating around right?

Seeing as how its only 82 outside today and the thing's not even keeping up, I doubt seriously its going to do the job when it hits the 90s and hundreds. I'm just trying to figure out if there's anything I should be checking further before calling the local dude out to service it again.

Another question: The steel end supports of the A-coil in the evaporator are badly rusted. Much more rusted than I'd expect from a 9 year old unit in the Texas Hill country. If it comes down to replacing the coils, or other expensive sounding labor, would it be more prudent to replace the POS with the matching air handler for the Ruud condenser, or to just replace the coils? This unit also has a piston in the air handler, if they need to replace it, would it be to my advantage to request an expansion valve instead? I've heard they're more efficient/work better, but I'll leave that decision up to people who know more than I do

[Cactus Bob]

MATCHING COIL TO UNIT IS OVERATED  a 2.5 ton coil to a 2.5 unit  with normal seer rateing of 10 -13  will allways work  . .your system is most likely low on freon due to a small leak somewhere  . if it stays small its not a big deal and you should be haveing you unit checked yearly anyway  , just keep a record of how much freon you loose yearly and if its a pound or so its no big deal if it starts to leak more it might be time for a coil or a new airhandler   .   BTW:  goodman is not a bad unit no better or worse than all the low price brands  reem-rudd.coleman , amana  ect   ALL UNITS BRAKEDOWN  and need service to keep them running properly ...... asd far a a orfice port vers TXV  ...... the orfice port never goes bad and the expansion valve does ..just one more thing to go bad and give trouble

[Pffester]

I agree with Cactus Bob.

Splashing & surging in the lines , and the coils frosting as you describe is always a sign of low charge. Have someone check it, top it off,  and keep track of it for a while.....

[ttuee2006]

Will do. Thanks for the help. If that doesn't fix it I'll post back.

[dkpd1581]

Your unit may be low on R22 possibly not from a leak but due to your mismatched unit.  One gets higher SEER ratings through several avenues.  One of the easiest is through a larger coil.  Look at R22 3 ton units at 10 SEER and look at the same tonnage at 13 SEER and you cant help but to notice how much larger the higher SEER is.  Greater coil face (hence the larger unit) means more refrigerant necessary to fill the thing.  Secondly, higher SEER is also achieved through lower compression ratios (the ratio of absolute pressure discharge divided by absolute pressure suction).  Obviously the suction pressure has to remain at a certain pressure/temperature.  Thus, we need to lower the discharge pressure - remember the lower the compression ratio (the lower we can get the top number) the more efficient.

If your new coil outside is larger it needs more refrigerant.  If your indoor coil is fed by a fixed orafice and the outdoor pressure is lower, the evaporator pressure will be lower without the help of a TXV metering device (the metering device is yet another way to get higher ratings along with Scroll compressors and variable speed motors).  Considering that your outdoor unit is larger (needs more refrigerant) and most likely your metering device is not TXV (cant adjust for the lower compression ratio and lower high side pressure) your unit is most likely acting under charged due to the mismatch.  Remember, your fixed meter device is looking for a certain pressure behind it and the newer higher efficiency condensor may not provide it.  Your unit may very well have a leak; however, I would look to the mismatched equipment first. 

Everyone has their opinions on matching coils and changing the evaporator coil and metering device when the condenosr is changed out in a higher SEER rating.  My experience from talking to the manufacturers and reading the test results of units PURPOSELY mismatched and tested for performance lead me to make sure they are matched.  The test results I have seen show that mismatched equipment will not even give the 10 SEER rating of the original unit - they waste money, electricity, and dont provide the comfort expected. 

HVAC is like a see-saw on the playground.  Its a balancing act to get the right action out of it.  Saying X-tons condensor mismatched to X-tons evaporator is the same as having one real skinny kid on one side of the see-saw and a one really fat kid on the other side.  Both are 3 years old - just like the unit halves are both the same tonnage.  The 2 kids are not rated or matched the same for capacity all things considered.  While its funny to watch on the playground, the same is not funny in your house when you are paying alot of money for equipment and the service it is supposed to provide.  Unfortunately, chances are good the unit will not perform to any standard that is worth while in its current configuration.  Just a thought.

Best of luck 

[ttuee2006]

Very interesting read dkpd. You inspired me to look more into the equipment I have in this house. I knew when I had the condenser unit replaced that it would be mismatched, and was warned that there could possibly be a problem later on. I had the original intention of replacing the air handler in February, but for financial constraints that hasn't happened.

I also find it interesting that as long as it is somewhat cool outside like it is today (about 78 for a high) the thing doesn't ice up. But when it gets hot like it was the other day, then it does. Just yet more reason to think there's something amuck here.

I also did some research on the units I have here. The Ruud condenser unit is a 3 ton, while the inside coil is rated at 2.5 ton. I also have model numbers which I should have posted before:

Ruud Condenser: UAND-030JAZ

Goodman Air Handler Model #: A32-10/ Part #: 15203-132

The compressor is a scroll compressor (and SOOO much quieter than the noisy recip unit it replaced), and the evaporator coils do have a fixed orifice. The original unit was a heat pump that never worked well, but the new condenser is just a regular A/C.

I know the condenser is a 13 SEER, but I have found no information anywhere to find out what the evaporator is rated at. Its almost like its a secret or something.

I am also fairly certain the original condenser unit was a 3 ton as well, but I have since lost the paperwork I had for it. I seem to recall the installer saying that the original unit was mismatched, and he installed the new 3 ton with the intention (as I did) to replace the indoor unit this past spring.

I will still call to have the freon levels checked, but I haven't seen any oily residue where a leak could be on any of the new plumbing from the condenser swap-out.